Top 15 Car Repairs by Mileage Range
Replacing the Battery
Most batteries have a lifespan of 30,000 to 50,000 miles and typically come with a three to five-year prorated warranty. It's important to check the battery cables and battery fluid (if applicable) during every oil change. Additionally, it's recommended to service the battery and terminals once a year, especially before the cold winter months arrive. For added peace of mind, even if you have jump starters in your car and access to roadside assistance, many people choose to replace their vehicle batteries every three years.
Replacing Coolant Hoses
When it’s time to flush the coolant system, it's also an excellent opportunity to replace the coolant hoses. Since the mid-1990s, most automotive coolants have had a lifespan of 50,000 miles or five years. Newer vehicles can have coolants that last up to 100,000 miles or ten years. The long-life properties of modern coolants, combined with extreme temperature fluctuations, can cause the inside of coolant hoses to crack and fail without warning.
Replacing Spark Plugs
Many manufacturers recommend spark plugs to last up to 30,000 miles, while others may suggest up to 100,000 miles depending on the material they are made from. It's a good idea to check for wear at the halfway mileage point or if your car is running rough or backfiring. If you're going to remove the spark plugs just to inspect them, consider replacing them while you're at it. With today’s sensitive engine monitoring systems, it's crucial to use the same type (copper, platinum, or iridium) and brand as recommended by your car's manufacturer.
Replacing the Timing Belt (and Water Pump)
Some manufacturers suggest replacing the timing belt every 30,000 miles, while others recommend it every 120,000 miles. It's always wise to replace the water pump when replacing the timing belt, even if it's not leaking. Several factors should be considered when deciding to replace a timing belt before the suggested mileage, including:
- A poor-running engine could indicate a loose timing belt.
- Engine misfires place undue stress on a timing belt, shortening its life.
- Missing teeth can cause a ticking or squealing noise.
- Frequent city driving, heavy acceleration, and extreme temperatures reduce the lifespan of timing belts.
- If you buy a used car with over 50,000 miles and the seller cannot provide proof that the timing belt was ever replaced.
Replacing the timing belt sooner than recommended is safer. “Driving a car with a worn timing belt can lead to the belt snapping, which can definitely cause catastrophic engine damage,” says Jorge Pinto, a mechanic based in New Jersey.
Replacing the Serpentine Belt
Serpentine belts can last between 50,000 and 100,000 miles. However, they wear slowly and may not show signs of wear but can still fail. Inspect the serpentine belt during every oil change for wear and tear, as well as deterioration from oil or coolant leaks. Serpentine belts are affected by the parts they drive, such as the air conditioning compressor, power steering pump, and alternator. They should be inspected regularly, especially if they are chirping or squealing.
Replacing the serpentine belt (and mounting brackets, pulleys, tensioners, and idler wheels if necessary) is a simple DIY job.
Replacing Brakes
There is no specific mileage recommendation for brakes and rotors. Brake wear depends on driving habits. City or stop-and-go driving can cause brakes to wear quickly, while highway driving can extend their lifespan. Inspect brake pads for wear when rotating tires (every six months or 6,000 miles), or if your brakes are noisy, locking up, pulling to one side, or have increased braking distance. The minimum thickness for brake pads is 3 mm to 4 mm—new pads are around 12 mm thick. Replace pads when the friction material reaches 6 mm or less.
Replacing brake pads is a DIY project.
Replacing Disc Brake Rotors
Under normal conditions, disc brake rotors should last between 30,000 and 70,000 miles or longer. Modern cars often have thinner rotors, so it's usually better and safer to replace them rather than resurface them. Overheating from worn brake pads, mechanical issues like binding calipers or bad wheel bearings, and improper installation of semimetallic pads can cause cracks, glazing, scoring, or excessive rotor wear. Rust buildup and over-tightened lug nuts can also warp rotors.
Replacing rotors yourself can save hundreds of dollars.
Replacing Shock Absorbers and Struts
Unless you drive recklessly, go off-road, or frequently encounter rough roads, shock absorbers should last about 50,000 miles or four to five years. MacPherson struts, which function similarly to shocks, provide a smoother ride and usually last 100,000 miles. Signs of worn shocks or struts include:
- Longer stopping distances
- Abnormal tire wear
- Strange noises
- Excessive vibration
Always have your car’s alignment checked after replacing shocks or struts. Rotate and balance your tires every 6,000 to 8,000 miles, and have the alignment checked every 12,000 to 15,000 miles. Depending on your car's model and your level of expertise, replacing shocks and struts yourself can save money and offer a sense of accomplishment.
Replacing Engine and Cabin Air Filters
Both engine and cabin filters should be replaced between 15,000 and 30,000 miles or one to two years. Driving conditions affect this, so check the air filter every 12,000 miles or during each oil change if you drive in dusty or city conditions. Replacing a dirty engine air filter can improve gas mileage and engine performance. A clogged cabin air filter affects passenger comfort and HVAC efficiency, leading to increased wear on expensive components.
Replacing these filters is a simple DIY task.
Replacing the Fuel Filter
Fuel filters are small but essential components of a vehicle’s fuel system. Some manufacturers recommend replacement between 20,000 to 40,000 miles (or two years), while others suggest 60,000 miles. In some cases, fuel filters never need replacing. Driving in dusty conditions, using poor-quality fuel, or moisture from condensation can cause the filter to clog and require replacement. Signs of a failing fuel filter include:
- Poor engine performance
- Hard starting
- Stalling
- Random misfire or rough idle
- Fuel system failures
In most cases, you can replace the fuel filter yourself.
Replacing the PCV Valve
The Positive Crankcase Ventilation (PCV) valve should be replaced every 24,000 miles or two years, depending on driving conditions. Check the PCV valve annually by removing it and shaking it; a functioning valve will rattle. Replace it if it doesn’t. Signs that the PCV valve needs replacement include:
- Poor acceleration
- Increased oil consumption or leaks due to pressure buildup
- Check engine light
- Excess smoke from the tailpipe
Replacing the PCV valve is a straightforward DIY task.
Replacing Oxygen (O2) Sensors
O2 sensors typically need replacement every 50,000 to 100,000 miles or five to six years. A failed sensor can impact fuel economy, drivability, and emissions, and may trigger the check engine light. Contamination from low-quality fuel, overheated catalytic converters, road debris, or slow-reacting sensors can lead to rich or lean air/fuel mixtures and possible backfiring.
Replacing an O2 sensor can be a DIY project, though identifying which sensors are faulty may require professional assistance.
Replacing the Gas Cap
Gas caps are critical components of the emission control system, yet they are often overlooked. Replace them every 50,000 miles or if the cap is cracked, the gasket is torn, or it won’t tighten properly. A loose gas cap can trigger the check engine light and set multiple trouble codes that require a scan tool to clear. Replacing a gas cap is quick and can save time and money.
Replacing Brake Fluid
Brake fluid degrades over time due to exposure to extreme temperatures, pressure, and moisture. This contamination turns brake fluid into a corrosive substance that can damage the hydraulic system. While you can top off old brake fluid, replacing all of it every 30,000 miles or two years ensures safe brake operation. If you have the right tools, replacing brake fluid is a DIY task. Otherwise, leave it to professionals.
Replacing Differential and Transfer Case Fluids
Most manufacturers recommend replacing differential and transfer case fluids between 30,000 and 60,000 miles, depending on driving conditions. Symptoms indicating the need for replacement include unusual noises from the differentials or transfer case, tire jumping, clicking sounds, or vibrations during turns. Checking for leaks during every oil change is essential. Replacing differential fluid is a DIY project, but transferring case fluid is best left to professionals.
FAQ
Based on mileage, when should I replace other fluids or parts in my car?
Family Handyman provides detailed guidance on replacing motor oil, automatic transmission fluid, power steering fluid, and other components.
Do turbocharged cars need fluids replaced more often?
Yes. Turbocharged engines run hotter and at higher RPMs, causing protective additives in motor oil and coolant to break down faster. This can lead to quicker wear on spark plugs and other components. Following the manufacturer’s maintenance schedule is crucial for turbocharged vehicles.
What is more important, miles or months?
Whichever comes first! If you drive 50,000 miles in less than 60 months, replace parts at 50,000 miles. If you drive less than 50,000 miles in 60 months, replace parts at 60 months.
About the Experts
Jorge Pinto is an auto mechanic based in New Jersey.